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The keratin in the [[Skin - Anatomy & Physiology#Epidermis|epidermis]], when cornified and thickened, is referred to as '''horn'''.  Horn is particulary resistant to mechanical and chemical damage.  The [[Skin - Anatomy & Physiology#Dermis|dermis]] of horn gives the structures their 3-D structure and shape.

The keratin in the [[Skin - Anatomy & Physiology#Epidermis|epidermis]], when cornified and thickened, is referred to as '''horn'''.  Horn is particulary resistant to mechanical and chemical damage.  The [[Skin - Anatomy & Physiology#Dermis|dermis]] of horn gives the structures their 3-D structure and shape. Cattle, some sheep, goats and antelope posess horns and these are permanent organs.  Deer posess '''antlers''', which are temporary organs that develop during the '''rutting season''' and are then shed.